The present invention relates to a bearing structure, and more particularly to a bearing structure adapted for oscillatory motion under heavy load.
The present invention is an improvement on the compound bearing disclosed in U.S. Pat. No. 2,683,637. That patent teaches a bearing structure between an inner member and an outer member consisting of a nylon or similar plastic insert ring interposed between the inner and outer members, and a pair of lubricant impregnated fabric annular members also disposed between the inner and outer members, one on each side of the nylon or other plastic insert ring. The structure is such that normal loads on the bearing are carried by the lubricant impregnated material, and heavy loads or shock loads on the bearing are taken principally by the plastic insert ring.
It has been found that bearings according to the aforesaid patent, although satisfactory and long-lived under average medium duty service, tend to deteriorate rapidly when subjected to extremely heavy loads, especially if subjected to heat simultaneously with heavy loads, and more particularly in assemblies where adverse conditions of heavy load and heat are accompanied by substantial vibrations and shocks and an exaggerated amount of twisting, or relative motion, between the inner member and the outer member of the bearing. Such extremely adverse conditions are particularly prevalent when spherical bearings are utilized as a junction between suspension members and frame members, such as shock absorber attachment means in heavy duty motor vehicles, for example military combat vehicles, which are generally poorly maintained and called upon to operate under extremely adverse conditions. It has been discovered that under such extreme adverse conditions, when the bearings are continuously subjected to rapid twisting cycles under extremely heavy loads with repeated high frequency shocks, prior art bearings tend to heat up and, when further subjected to heat from the ambient, they deteriorate rapidly. The lubricant impregnating the fabric annular members becomes very fluid and extrudes from the fabric, and the extreme heat chars the fabric annular members and destroys the nylon or other plastic insert ring. It has also been discovered that because the prior art bearings are pre-loaded during manufacturing, they are relatively tight when new, and thus they provide a relatively stiff connection between the joined components and tend to generate heat when the engaged surfaces of the various components of the bearings are displaced relative to each other, due to the relatively high co-efficient of friction between the bearing element surfaces.